A flip chip bonding method is known as a method for connecting a plurality of electronic parts (for example, IC chips, rigid boards, flexible boards, and the like) having electrode terminals. In the flip chip bonding method, electrode terminals of a plurality of electronic parts are connected together in a state where the electrode terminals are opposed.
As an example of such a flip chip bonding method, an ultrasonic connection method is known. In this method, electrode terminals of a plurality of electronic parts are brought into contact with each other. Next, the contact portion between electrode terminals is oscillated by an ultrasonic wave. Thereby, the electrode terminals are connected together. In this method, the electrode terminals of both electronic parts are formed of gold. Next, filler (what is called underfill) is put in a space around the connection portion, and is hardened.
As another example of the flip chip bonding method, a eutectic method is known. In this method, electrode terminals of a plurality of electronic parts are brought into contact with each other. Next, the contact portion between electrode terminals is heated. Thereby, the electrode terminals form a eutectic, and are connected together. In this method, for example, the electrode terminal of one electronic part is formed of gold, and the electrode terminal of the other electronic part is formed of tin. Next, filler (what is called underfill) is put in a space around the connection portion, and is hardened.
However, in the ultrasonic connection method, the electrode terminal is largely oscillated by an ultrasonic weave, and therefore connection failure, a short circuit, etc. may occur. Furthermore, an electrode terminal to which the ultrasonic connection method can be applied needs to be formed of an expensive material such as gold, and therefore the cost is increased. Furthermore, the putting-in and hardening of filler are needed, and therefore the cost is increased also in this respect. Moreover, the number of processes is increased.
On the other hand, in the eutectic method, the connection portion between electrode terminals is heated, and the heating temperature at this time is very high. For example, the heating temperature is approximately 400° C. Hence, in the case where the electronic part is a flexible board, the flexible board may deform during heating. If the flexible board is deformed, the position of the electrode terminal on the flexible board etc. may be shifted. Therefore, connection failure, a short circuit, etc. may occur. Furthermore, there is also a problem regarding filler like in the ultrasonic connection method.
Thus, these days, for example as disclosed in Patent Literatures 1 and 2, a method of connecting electrode terminals together by anisotropic conductive connection using an anisotropic conductive film is drawing attention as a flip chip bonding method. In this method, an ultrasonic wave is not needed, and therefore a problem regarding an ultrasonic wave does not occur. Furthermore, although also a connection method using an anisotropic conductive film needs a heating process, the heating temperature is lower than in the eutectic method. Moreover, a hardenable resin forming the anisotropic conductive film functions as filler, and therefore the process of putting in and hardening filler separately is not needed.